1. Field of the Invention
The present invention relates to an anchoring device for a corrosion-resistant tension member, particularly an inclined cable for a cable-stayed bridge having a plurality of tension elements such as steel rods, steel wires, or steel strands, which are arranged inside a tube-shaped sheath. The tension elements are embedded in a corrosion-resistant substance, with each being arranged in a plastic sheath. Each anchoring device has an anchor body, which is provided with bores for the tension elements to pass through. To a side of the anchor body that is opposite from the exposed side, at least one sealing plate is attached, through which the tension elements are threaded, and next to which a perforated disk is arranged that serves as a spacer for the individual elements.
2. Description of the Background Art
With conventional tension members, so-called monostrands are frequently used as tension elements, that is, strands made of seven steel wires, each being arranged inside a sheath made of plastic, for example, polyethylene, and which are embedded in a corrosion-resistant substance, for example, grease, that fills the cavities between the wires and the ring space between the strand and the sheath. The anchorage of the strands usually includes anchor plates made of steel, with conical, and subsequently cylindrical bores, through which the strands are threaded and in which they are anchored with multiple-part ring wedges. To anchor the strands, it is, however, always necessary to expose the strands in the area of the anchorage by removing the sheaths, so that the anchorage wedges can directly grip the strands.
With a known anchoring device of this kind, the sheaths extend into an anchor pot that is filled with a corrosion-resistant substance, the bottom of the anchor pot having a multitude of openings, the number of openings being equal to the number of strands, through which the strands with their sheaths are fed (DE-A-37 34 954). There is no seal provided because the cavity outside the anchor pot and inside the anchor tube is filled in with cement mortar.
In order to seal off the cavity in the anchoring area, which is to be filled with a corrosion-resistant substance, as tightly as possible against the cavity in the exposed area of the tension member, when it is not going to be filled with hardened material, for example, cement mortar, it is known to arrange a sealing plate that is made of an elastic, ductile material, for example, Neoprene, on the side of the anchor plate that is opposite of the exposed side (EP 0 703 326 B1). The individual strands in their sheaths are threaded through a perforated disk, which serves as a spacer, and the sealing plate to, that is, through the anchor plate so that the corrosion-resistant substance enclosing the strands inside their sheaths directly connects with the material that fills the bores in the anchor plate.
With threaded bolts, which extend through the anchor plate, the sealing plate, and the perforated disk, which follows thereafter, a surface pressure is applied to the sealing plate via the perforated disk that, due to the lateral deformation of the sealing plate resulting therefrom, causes the sealing off of the cavity against the sheaths of the strands.
With this arrangement, not only the sealing plate but also the plastic perforated disk are compressed; a three-dimensional stress condition is created with the result, that the sealing plate is deformed plastically in a lateral direction, thus enclosing the strands firmly. Due to a buckling of the sealing plate and a shifting connected therewith, the perforated disk at the same time changes its position in the direction of the anchor plate; this also causes a repositioning of the reversing point of the strands, which have to be returned from an expanded position towards the anchorage to its former parallel position.
When individual strands need to be replaced, their tension must be decreased. Before loosening the ring wedges of the strands, the threaded bolts, which compress the perforated disk, the sealing plate, and the anchor plate, must be loosened. Due to both, the lateral deformations that took place and the effect of the reversing forces of the strands on the perforated disk, but also as a result of age-related shifting of the plastic material, the perforated disk cannot return to its original position, when the surface pressure on the plates decreases after the threaded bolts are loosened, without additional expenditure of energy; even less so since in this case, the tube-shaped sheath in the area adjacent to the anchor plate is an anchor tube of conical shape corresponding to the expansion of the strands towards the anchor plate. Therefore, a replacement of individual strands requires the dismantling of the entire anchor plate; otherwise there is the danger that the deformed sealing plate is damaged when the strands are pulled.